H2O
Unit 5
“Chemical Names
and Formulas”
Chemistry
Troy High School
Mr. Blake
Section 9.1
Naming Ions
•
Atoms and Ions
are
electrically neutral.
– Same number of p+ and e-
•
- atoms with a charge (+ or -)
• Made by gaining or losing
.
– Only electrons can move
An Anion is…
• A negative ion =
electrons.
• Nonmetals gain electrons.
• Charge is written as a superscript on the right.
1F
2O
Has gained
electron
(-ide is new ending =
Gained
electrons (
)
)
A Cation is…
•
•
A positive ion =
electrons.
lose electrons
1+
K
2+
Ca
Has lost
electron
(no name change for positive ions)
Has lost
electrons
Predicting Ionic Charges
Group 1A: Lose
H1+ Li1+
electron to form
Na1+ K1+ Rb1+
ions
Predicting Ionic Charges
Group 2A: Loses
electrons to form
Be2+ Mg2+ Ca2+ Sr2+ Ba2+
ions
Predicting Ionic Charges
B3+
Al3+
Ga3+
Group 3A: Loses
electrons to form
ions
Predicting Ionic Charges
Group 4A: Do they
lose 4 electrons or
gain 4 electrons?
!
Group 4A elements
rarely form ions (they
tend to share)
Predicting Ionic Charges
N3- Nitride
P3-
Phosphide
As3- Arsenide
Group 5A: Gains _
electrons to form
ions
Predicting Ionic Charges
O2- Oxide
S2-
Sulfide
Se2- Selenide
Group 6A: Gains
electrons to
form
ions
Predicting Ionic Charges
F1- Fluoride
Cl1- Chloride
Group 7A: Gains
Br1- Bromide
_ electron to
I1-Iodide
form
ions
Predicting Ionic Charges
Group 8A: Stable noble gases
form ions!
Predicting Ionic Charges
Group B elements: Many transition elements
have
possible charge.
Use of Roman numerals
to show charges
Iron (II) =
Iron (III) =
Naming Cations
•
system –
use roman numerals in
parenthesis to indicate the
charge value
Naming cations
• If the charge is always the
(like in the Group A metals) just write
the
of the metal.
– Calcium = 𝐶𝑎+2
•
metals can have
more than one type of charge.
– Indicate charge as roman numeral in
after the name
of the metal (Table 9.2, p.255)
– Iron (IV) =
Predicting Ionic Charges
Some
elements also
have more than one possible charge.
Tin (II) =
Tin (IV) =
Lead (
Lead (
) = Pb2+
) = Pb 4+
Predicting Ionic Charges
Group elements: Some transition elements
have only one possible oxidation state, such
as these three: **Do not use roman
numerals for these
Silver =
Zinc =
Cadmium =
Practice by naming these:
•
•
•
•
•
•
•
Na+
Ca2+
Al3+
Fe3+
Fe2+
Pb2+
Li+
Write symbols for these:
• Potassium ion
• Magnesium ion
• Copper (II) ion
• Chromium (IV) ion
• Barium ion
• Mercury (II) ion
Naming Anions
• Anions are
the same charge
• Change the ending to
_
1•F
a Fluorine atom will
become a
ion.
Practice by naming these:
• Cl3•N
• Br
• O2• Ga3+
Write symbols for these:
• Sulfide ion
• Iodide ion
• Phosphide ion
• Strontium ion
Polyatomic ions are…
• Groups of atoms that
together,
have an
charge, and one name.
• Usually end in –
or _
• Acetate: C2H3O2
• Nitr
: NO3
• Nitr
: NO2-
• Permanganate: MnO4• Hydroxide: OH- and Cyanide: CN-?
Know Table 9.3 on page 257
• Sulf
: SO42-
• Sulf
: SO32-
• Carbonate: CO32• Chromate:
CrO42-
• Dichromate:
Cr2O72-
• Phosph
: PO43-
• Phosph
: PO33-
• Ammonium: NH41+
(One of the few positive
polyatomic ions)
H + Polyatomic ion =….
•If the polyatomic ion begins with H, then put
“hydrogen” in front of the polyatomic ion:
H1+
+
CO32- →
HCO31-
hydrogen + carbonate → hydrogen carbonate ion
• HSO3
• HPO4
• HCO3
Helpful Hints on Oxy-Anions
1. _________:
2. _________:
smaller # of oxygen
larger # of oxygen
Ex.
NO3-
____________________________
NO2-
____________________________
SO42-
____________________________
SO32-
____________________________
A Guide to Determine Whether the –ate Formula is
–XO3 or –XO4:
1
2
13
14
15
16
18
17
1
2
B
3
4
5
6
Transition
Metals
C
N
Si
P
S
Cl
As
Se
Br
I
Section 9.2 Naming
and Writing
Formulas for Ionic
Compounds
Writing Ionic Compound Formulas
Example: Iron (III) chloride
1. Write the cation and
anion with CHARGES!
2. Balance charges using
the criss-cross method
with subscripts, if
necessary. Use
parentheses if you need
more than one of a
polyatomic ion to balance
subscripts.
Writing Ionic Compound Formulas
Example: Aluminum sulfide
1. Write the cation and
anion with CHARGES!
2. Balance charges using
the criss-cross method
with subscripts, if
necessary. Use
parentheses if you need
more than one of a
polyatomic ion to balance
subscripts.
Writing Ionic Compound Formulas
Example: Zinc hydroxide
1. Write the cation and
anion with CHARGES!
2. Balance charges using
the criss-cross method
with subscripts, if
necessary. Use
parentheses if you need
more than one of a
polyatomic ion to balance
subscripts.
Writing Ionic Compound
Formulas
Example: Magnesium carbonate (note the 2 word name)
1. Write the formulas for the
cation and anion, including
CHARGES!
2. Check to see if charges are
balanced.
Mg2+ CO32They are balanced!
Writing Ionic Compound Formulas
Example: Barium nitrate (note the 2 word name)
1. Write the cation and
anion with CHARGES!
2. Balance charges using
the criss-cross method
with subscripts, if
necessary. Use
parentheses if you need
more than one of a
polyatomic ion to balance
subscripts.
Writing Ionic Compound Formulas
Example: Ammonium sulfate
1. Write the cation and
anion with CHARGES!
2. Balance charges using
the criss-cross method
with subscripts, if
necessary. Use
parentheses if you need
more than one of a
polyatomic ion to balance
subscripts.
Writing Ionic Compound
Formulas
Example: Aluminum phosphate
1. Write the formulas
for the cation and anion,
including CHARGES!
2. Check to see if
charges are
balanced.
3+
Al
PO4
3-
They ARE balanced!
Naming Ionic Compounds
• 1. Cation
, then anion
• 2. Monatomic cation = name of the
element
• Ca2+ =
ion
• 3. Monatomic anion = root + -ide
• Cl- =
• CaCl2 =
Naming Ionic Compounds
(Metals with multiple oxidation states)
• If the metal can have more than one
charge (
), use a
Roman numeral in their name:
PbCl2  use the
to find the
charge on the cation
(chloride is always 1-)
is the lead (
PbCl2 = lead (
) cation
) chloride
Things to look for:
1) If cations have ( ), the number
in parenthesis is their
.
2) If anions end in –ide, they are
probably off the periodic table
(
)
3) If anion ends in -ate or –ite,
then it is
Practice by writing the formula or
name as required…
• Iron (II) Phosphate
• Stannous Fluoride
• Potassium Sulfide
• Ammonium Chromate
• MgSO4
• FeCl3
Section 9.3
Naming and Writing
Formulas for
Molecular
Compounds
Molecular compounds are…
• Made of only
• Smallest part is a
• Can’t use charges to figure out
how many of each atom (there
are no charges present / they
share electrons)
Molecular compounds are easier!
•
compounds use
to determine how many of each.
• Figure out charges and criss-cross numbers.
• Molecular compounds: the name tells
you the number of atoms.
• Uses
to tell you the
exact number of each element present!
Prefixes (Table 9.4, p.269)
•
•
•
•
•
•
•
•
1 = mono2 = di3=
4 = tetra5=
6 = hexa7 = hepta8 = octa-
• 9 = nona• 10 =
Prefixes
• To write the name, include:
Prefix + name -ide
• One exception is we don’t write
if there is only
of
the
element.
• Normally, we do not have double vowels
when writing names (oa oo)
Practice by naming these:
• N2O
• NO2
• Cl2O7
• CBr4
• CO2
• BaCl2
Write formulas for these:
• diphosphorus pentoxide
• tetraiodine nonoxide
• sulfur hexafluoride
• nitrogen trioxide
• carbon tetrahydride
• phosphorus trifluoride
• aluminum chloride
(Ionic compound)
Section 9.4
Naming and Writing
Formulas for Acids
and Bases
Acids are…
• Compounds that give off
ions (H+)
when dissolved in water
(the Arrhenius definition)
• Formula starts with
.
• Always be some Hydrogen
next to an
.
•
determines the name.
Rules for Naming acids: Name it
as a normal compound first
• If the anion attached to hydrogen ends in
-ide, put the prefix
and change -ide to -
acid
• In other words, if it’s just Hydrogen and one other nonmetal
HCl =
• H2S =
•
acid
acid
Naming Acids
If the anion has oxygen in it, then it ends in
-ate or -ite
2) Change -ate to -ic acid (use no prefix)
• Example: HNO3
Hydrogen + nitrate =
•
3) Change -ite to -ous acid (use no prefix)
• Example: HNO2
Hydrogen + nitrite =
Naming Acids
Normal ending
Acid name is…
____-ide
hydro-___-ic acid
____-ate
_____-ic acid
____-ite
_____-ous acid
Practice by naming these:
• HF
• H3P
• H2SO4
• H2SO3
• HCN
• H3PO4
Writing Acid Formulas – in reverse!
•
•
•
Hydrogen will be listed first
The name will tell you the
Be sure the charges cancel out.
• Starts with hydro?
• Anion is
ends in –ide
,
• No hydro?
1) -ate anion comes
from –
ending
2) -ite anion comes
from –
ending
Write formulas for these:
• hydroiodic acid
• chloric acid
• carbonic acid
• phosphorous acid
• hydrobromic acid
Names and Formulas for Bases
• Base - an ionic compound that produces
ions (
)
when dissolved in water (the Arrhenius definition)
• Named the same way as other ionic
compounds:
– Name of cation (
) followed by
name of anion (which will be
).
Names and Formulas for Bases
• NaOH =
• Ca(OH)2 =
• To write the formula:
1) Write symbol for metal cation
2) Followed by hydroxide ion (OH1-)
3) Use criss-cross method to balance the
charges.
Practice by writing the formula
for the following:
• Magnesium hydroxide
• Iron (III) hydroxide
• Zinc hydroxide
Section 9.5
The Laws
Governing
Formulas and
Names
Some Laws:
Law of
Proportionsin a sample of a chemical compound,
the
of the
are always
in the
proportions.
In every molecule of H2O (water), the
mass ratio of H:O is 1:8
Some Laws:
Law of
ProportionsWhenever two elements form
than one
compound, the
masses of one
element that combine with the
mass
of the other element are in the ratio of
small
.
H2O (water) and H2O2 (hydrogen peroxide)
2:1
2:2
2g:16g
2g:32g
• https://www.youtube.com/watch?v=0OOcp
iTiXzM
• Law of Definite Proportions - Law of
Multiple Proportions
• by Brightstorm
Summary of Naming and
Formula Writing
• For naming, follow the
flowchart- Figure 9.20, page
277
• For writing formulas, follow the
flowchart from Figure 9.22,
page 278
Helpful to remember...
1. In ionic compounds, the net charge is
(criss-cross method)
2. Put -ide at the end of monatomic
3. An -ite or -ate ending means there is a
ion that
has
4. Prefixes generally mean
;
they show the number of each atom
_
Helpful to remember...
5. A Roman numeral after the
name of a cation is the
of the cation